This invention is intended to improve the quality of stormwater runoff from developed impervious surfaces. Stormwater runoff from impervious surfaces like parking lots contains many different contaminants, such as sediments, nutrients, heavy metals, and organic chemicals. In most developed areas of the United States, this runoff is collected in pipes and discharged directly into a stream or other water body. The present invention provides a means by which some of the environmentally detrimental constituents may be removed from the water.
During the last ten years, a new industry has developed to treat stormwater runoff. To date, the main focus of this industry has been removing suspended solids from the water. Solids can be removed by physical separation, which is most easily achieved by reducing water velocities and allowing the solids to settle out of the water. This is the theory behind the ponds, sediment basins, and hydrodynamic separators that comprise the majority of commercially available stormwater treatment devices. Much of the pollution in stormwater runoff, however, is not suspended, but instead dissolved in the water. These dissolved contaminants require more effective treatment, hence a filter is often used. However, all of the devices now in use become quite inefficient when there is a high rate of flow through them.
Assume that the runoff water from a filling station has both suspended contaminants and dissolved contaminants. This runoff water will be cleaned by my invention as follows: Such runoff water first enters a gravity particle separator such as is taught in my U.S. Pat. Nos. 5,746,911 and 6,264,835. The disclosures of these patents are incorporated herein by reference. This particle separator removes suspended contaminants from the runoff water. The output of the particle separator is fed to a reservoir which is so big that it will hold all of the water from a prolonged hard rain lasting several hours. The output of the reservoir is fed through a limiter to a filter which removes dissolved contaminants from the water. The filter conforms to my copending patent application Ser. No. 10/040,611, filed Jan. 9, 2002, now U.S. Pat. No. 6,869,528 of Mar. 22, 2005 (the disclosure of this patent is incorporated herein by reference), see also patent application publication US/2002/0117435 A1. Such a filter is inefficient if the flow therethrough exceeds a given rate. The aforesaid limiter prevents the flow to the filter from exceeding said given rate.